美国德克萨斯大学Alan M. Lambowitz课题组揭示第二组内含子类逆转录酶在双链断裂修复中的功能。这一研究成果于2022年9月15日发表在国际学术期刊《细胞》上。

研究人员发现铜绿假单胞菌第二组内含子编码的逆转录酶（G2L4 RT）的活性位点是YIDD而不是YADD，在其原生宿主中和在大肠杆菌中表达时，可用于DNA修复。G2L4 RT具有与人类DNA修复聚合酶θ惊人相似的生化活性，并通过微组学介导的末端连接（MMEJ）将其用于易位DNA合成和双链断裂修复（DSBR）。

研究人员还发现，第二组内含子RT可以在DNA修复中发挥类似的功能，其活性位点的互换显示异亮氨酸有利于MMEJ，而丙氨酸有利于两种酶的引物延伸。这些DNA修复功能利用了非LTR反义词RT的保守结构特征，包括人类LINE-1和其他真核生物的非LTR反义词RT，表明这种酶可能具有在多种生物体中发挥DSBR功能的固有能力。

据介绍，细菌编码的RT功能不明，与第二组内含子编码的RT密切相关。

附：英文原文

Title: Group II intron-like reverse transcriptases function in double-strand break repair

Author: Seung Kuk Park, Georg Mohr, Jun Yao, Rick Russell, Alan M. Lambowitz

Issue&Volume: 2022-09-15

Abstract: Bacteria encode reverse transcriptases (RTs) of unknown function that are closelyrelated to group II intron-encoded RTs. We found that a Pseudomonas aeruginosa group II intron-like RT (G2L4 RT) with YIDD instead of YADD at its active site functionsin DNA repair in its native host and when expressed in Escherichia coli. G2L4 RT has biochemical activities strikingly similar to those of human DNA repairpolymerase θ and uses them for translesion DNA synthesis and double-strand break repair(DSBR) via microhomology-mediated end-joining (MMEJ). We also found that a group IIintron RT can function similarly in DNA repair, with reciprocal active-site substitutionsshowing isoleucine favors MMEJ and alanine favors primer extension in both enzymes.These DNA repair functions utilize conserved structural features of non-LTR-retroelementRTs, including human LINE-1 and other eukaryotic non-LTR-retrotransposon RTs, suggestingsuch enzymes may have inherent ability to function in DSBR in a wide range of organisms.

DOI: 10.1016/j.cell.2022.08.014

Source: https://www.cell.com/cell/fulltext/S0092-8674(22)01063-7